We have been awarded first place in the Journal of Wound Care awards 2018 for Innovation in Surgical Site Infection. This was for our work in collaboration with Prof C. Childs (Sheffield Hallam University) on thermal imaging Cesarean Section wounds to predict future infections and reduce the use of antibiotics: http://www.jwcawards.com/

Latest Research

Sensing of electromagnetic waves has revolutionised society through diverse areas such as communications, manufacturing, healthcare and imaging. Below are some of our latest contributions to the field. Please paste the doi into a search engine to access the full articles

Accurate quantitative temperature measurements are difficult to achieve using focal-plane array sensors. This is due to reflections inside the instrument and the difficulty of calibrating a matrix of pixels as identical radiation thermometers. Size-of-source effect (SSE), which is the dependence of an infrared temperature measurement on the area surrounding the target area, is a major contributor to this problem and cannot be reduced using glare stops. Measurements are affected by power received from outside the field-of-view (FOV), leading to increased measurement uncertainty. In this work, we present a micromechanical systems (MEMS) mirror based scanning thermal imaging camera with reduced measurement uncertainty compared to focal-plane array based systems. We demonstrate our flexible imaging approach using a Si avalanche photodiode (APD), which utilises high internal gain to enable the measurement of lower target temperatures with an effective wavelength of 1 μm and compare results with a Si photodiode. We compare measurements from our APD thermal imaging instrument against a commercial bolometer based focal-plane array camera. Our scanning approach results in a reduction in SSE related temperature error by 66 °C for the measurement of a spatially uniform 800 °C target when the target aperture diameter is increased from 10 to 20 mm. We also find that our APD instrument is capable of measuring target temperatures below 700 °C, over these near infrared wavelengths, with D* related measurement uncertainty of ± 0.5 °C.

doi:

Smartphone spectrometers2018

McGonigle, AJS and Wilkes, TC and Pering, TD and Willmott, JR and Cook, JM and Mims, FM and Parisi, AV

CCBY Silicon-based Single Photon Avalanche Diodes (SPADs) are widely used as single photon detectors of visible and near infrared photons. There has however been a lack of models accurately interpreting the physics of impact ionization (the mechanism behind avalanche breakdown) for these devices. In this work, we present a statistical simulation model for silicon SPADs that is capable of predicting breakdown probability, mean time to breakdown and timing jitter. Our model inherently incorporates carriers \& #x0027; dead space due to phonon scattering and allows for non-uniform electric fields. Model validation included avalanche gain, excess noise factor, breakdown voltage, breakdown probability, and timing statistics. Simulating an n on-p and a p-on-n SPAD design using our model, we found that the n-on-p design offers significantly improved mean time to breakdown and timing jitter characteristics. For a breakdown probability of 0.5, mean time to breakdown and timing jitter from the n-on-p design were 3 and 4 times smaller compared to those from the p on n design. The data reported in this paper is available from the ORDA digital repository (DOI: 10.15131/shef.data.4823248).

Wilkes, T and Pering, T and McGonigle, A and Tamburello, G and Willmott, J

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doi:10.3390/rs9010027

Ultraviolet Imaging with Low Cost Smartphone Sensors: Development and Application of a Raspberry Pi-Based UV Camera2016

Wilkes, TC and McGonigle, AJS and Pering, TD and Taggart, AJ and White, BS and Bryant, RG and Willmott, JR

Here, we report, for what we believe to be the first time, on the modification of a low cost sensor, designed for the smartphone camera market, to develop an ultraviolet (UV) camera system. This was achieved via adaptation of Raspberry Pi cameras, which are based on back-illuminated complementary metal-oxide semiconductor (CMOS) sensors, and we demonstrated the utility of these devices for applications at wavelengths as low as 310 nm, by remotely sensing power station smokestack emissions in this spectral region. Given the very low cost of these units, ≈ USD 25, they are suitable for widespread proliferation in a variety of UV imaging applications, e.g., in atmospheric science, volcanology, forensics and surface smoothness measurements.

Xie, S and Zhou, X and Zhang, S and Thomson, DJ and Chen, X and Reed, GT and Ng, JS and Tan, CH

Increasing reliance on the Internet places greater and greater demands for high -speed optical communication systems. Increasing their data transfer rate allows more data to be transferred over existing links. With optical receivers being essential to all optical links, bandwidth performance of key components in receivers, such as avalanche photodiodes (APDs), must be improved. The APDs rely on In0.53Ga0.47As (grown lattice-matched to InP substrates) to efficiently absorb and detect the optical signals with 1310 or 1550 nm wavelength

doi:10.1364/OE.24.024242

Thermal territories of the abdomen after caesarean section birth: Infrared thermography and analysis2016

Childs, C and Siraj, MR and Fair, FJ and Selvan, AN and Soltani, H and Wilmott, J and Farrell, T